An implantable blood pump used as a mechanical circulatory support device or “MCSD” includes a pumping mechanism to move blood. The pumping mechanism may be a radial flow pump, such as the HVAD® Pump manufactured by HeartWare, Inc. in Miami Lakes, Fla., USA. The HVAD® Pump is further discussed in U.S. Pat. No. 8,512,013, the disclosure of which is hereby incorporated herein in its entirety. Alternatively, the pumping mechanism may be an axial flow pump, such as the MVAD® Pump, also manufactured by HeartWare, Inc., and the pumps described in U.S. Pat. Nos. 7,972,122, 8,007,254 and 8,419,609, the disclosures of which are also hereby incorporated herein in their entirety, or any other pump suitable for providing vascular assistance. In operation, the blood pump draws blood from a source such as the right ventricle, left ventricle, right atrium, or left atrium of a patient's heart and propels the blood into an artery such as the patient's ascending aorta or peripheral artery. Due to the nature of the application, the pumping mechanism must be highly reliable. Patient comfort is also a significant consideration. In addition to the pumping mechanism, the device may include a controller and the drive electronics for the pumping mechanism. The controller and drive electronics may receive power from an external power source. That power may be used to drive the pumping mechanism.
The control circuit may be configured to monitor operation of the blood pump. During such monitoring, if the control circuit detects the presence of an undesirable condition at either the blood pump or the patient's heart (near the blood pump), the control circuit may take action to address the undesirable condition, e.g., provide an alert to the patient or clinician, control operation of a motor of the pump to attempt to clear the undesirable condition, etc. In some cases the patient's heart has sufficient pumping capacity to sustain life for at least a limited time. For instance, where the blood pump provides only partial support to the patient, stoppage of the pump may cause the patient to revert back to a diseased condition or state (e.g., due to degenerative heart failure), in which the patient's heart can sustain life for at least a limited time. In such cases, controlling operation of the pump may involve stopping operation of the pump until the undesirable condition clears. Operation of the pump may then be automatically restarted or manually restarted, directly or indirectly, by the patient (e.g., providing power the pump) or by a clinician.
Generally, where operation of the pump has stopped, it may be desirable to provide the pump with a way of promptly, manually restarting so that it may resume providing its intended assistance to the patient. However, under some circumstances, it may be undesirable to restart operation of the pump. For instance, if the pump is idle for a long enough time, there may an increased risk of thrombosis in the pump, such that sudden restarting of the pump may propel a clot into the blood stream of the patient. Under such circumstances, it may be necessary to initially examine and subsequently monitor the patient to ensure that restarting the pump does not pose a risk to the patient's health. It may also be desirable under such circumstances to prevent the patient or a clinician from restarting the pump without first examining or monitoring the patient, or at least without making an informed decision given the risk associated with restarting the pump after an extended cessation.